This invention relates to electrical circuit testing and more particularly to AC/DC circuit testing at construction and maintenance sites where rugged testing equipment is required. Still more particularly the invention relates to apparatus and method for conveniently detecting circuit shorts, establishing continuity, indicating resistance throughout a plurality of ranges, measuring voltage and detecting voltage polarity.
It is well known to provide electrical testing apparatus which measures and indicates voltage, indicates polarity, and checks circuit continuity. In most cases, electrical faults can be detected by using a tester that measures the expected value of voltage and checks the continuity of a circuit under test. However, it is often necessary to be able to distinguish between short-circuits and circuits having low resistance values. For example, motor windings, relay coils, and transformer windings typically have low resistance values. It is of critical importance to be able to determine whether these devices are short-circuited before applying power to them.
However, typical continuity testers will not differentiate between a circuit having a low resistance value, such as 100 ohms to 10,000 ohms, and a circuit with a short measuring about ten ohms or less. A typical tester of such a type is disclosed in Sirasud U.S. Pat. No. 4,825,150. It is an object of this invention to provide a tester having all the capabilities of such prior art devices, as well as continuity testing capable of distinguishing between short-circuit conditions and low-resistance conditions, and providing a discernible indication of such conditions.